1994 рік

This paper reports the conductivities of polyphenylquinoxaline (PPQ) doped with aqueous H2SO 4. The highest conductivity of doped PPQ is 4.5 x 10-2Scm -1 obtained by the four-probe method at room temperature. The influence of concentration of aq. H2SO4 and doping time on the conductivity of doped PPQ is discussed. The structures of doped and undoped PPQ were confirmed by Fourier-transform infra-red, ultra-violet and X-ray photoelectron spectroscopies, electron spin resonance and elemental analysis. Also, the stability of the conductivity value was examined

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The water uptake and swelling behaviour of physically crosslinked, inhomogeneous poly(acrylonitrileacrylamide- acrylic acid) hydrogels from 10 to 60°C were determined by gravimetry/differential scanning calorimetry and volume measurement, respectively. The contents of water and its non-bound portion were found to reach a minimum value at acrylamide content around 33.5 mol%, at which the water uptake of this gel does not vary with the temperature. The non-bound water was found to decrease gradually and then increase with increasing amide concentration. The duration of the post-gelation treatment between - 10 and 10°C was also shown to be one of the factors affecting the extent of the water uptake in gels. The critical endpoint temperatures (T~s) of hydrogels, obtained from volume phase transition data upon changing the acetone concentration in aqueous solutions at various temperatures, were shown to decrease with the increasing acid or amide contents. The water uptake for gels with lower amide contents decreases with increasing temperature. However, there is an opposite trend for water uptake in gels with higher amide content, and the critical points on the plots of the amount of water uptake versus temperature appear at a temperature equal to To.

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Various homopolyamides and copolyamides bearing olefinic bonds and pendent cyano groups were prepared by reacting aromatic diamines with the acid chloride of 1,4-bis(2-cyano-2-carboxyvinyl)benzene. In addition, the latter reacted with aniline to afford a model diamide. The monomers were characterized by infra-red and tH nuclear magnetic resonance spectroscopy, as well as by elemental analyses. Characterization of polyamides was accomplished by infra-red spectroscopy, differential thermal analysis, thermogravimetric analysis, isothermal gravimetric analysis and inherent-viscosity measurements. The synthesized homopolyamides were soluble in polar aprotic solvents and certain strong inorganic and organic acids. Upon thermal curing, crosslinked polymers were obtained. The thermal stabilities of cured resins were correlated with the curing conditions and their composition. They were stable up to 391-407°C in N 2 or air and afforded anaerobic char yield of 64-70% at 800°C.

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This paper evaluates an effective interfacial agent, poly(propylene-co-l-hexen-6-ol) (hydroxylated polypropylene, PP-OH), that improves the adhesion between polypropylene (PP) and glass. Owing to the unique brush-like microstructure of PP-OH, with flexible primary hydroxy groups and long sequences of propylene units, the hydroxy groups effectively form chemical bonds with the free silanol groups on the glass surface, and the PP segments cocrystallize with isotactic PP. The strong interfacial interactions are shown in 90 ° peel tests of PP/glass laminates. Both scanning electron microscopy and contact-angle studies on the fracture surfaces indicate no adhesive failure during peeling. In addition, differential scanning calorimetry studies demonstrate the cocrystallization between PP and PP-OH, and reflection infra-red results provide direct evidence of chemical bonding between PP-OH and glass surfaces.

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This paper discusses the miscibility of cellulose/poly(ethylene oxide) (PEO) blend systems from the view point of the relationship between hydrogen bond formation and regiochemistry of hydroxyl groups in cellulose. Thermodynamic examination of the systems using 2,3-di-0- and 6-O-methylcelluloses (23MC and 6MC) as cellulose model compounds was carried out by differential scanning calorimetry. The values of two parameters, interaction energy density characteristic, B, and interaction parameter, Z12, assessed by the thermodynamic analyses indicated evidence of polymer-polymer interaction in 23MC/PEO blends and lack of interaction between 6MC and PEO in their blends. Optical microscopic observation of the blend systems revealed the same phenomena. Results of the two investigations support our proposal of a regiochemical effect of hydroxyl groups in cellulose analysed by Fourier transform i.r. spectroscopy; that is, primary hydroxyl groups at the C6 position of the glucose unit of cellulose interact predominantly with ether oxygen in PEO, while secondary hydroxyls at the C2 and C3 positions are not engaged in hydrogen bonding. However, in pure cellulose/PEO blend each negative magnitude of the values was much larger than the sum of the values of each parameter for the 23MC/PEO and 6MC/PEO blends, indicating the presence of secondary polymer-polymer interaction.

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Starting from aliphatic polyesters of thiodipropionic acid and linear glycols containing ethylene oxide groups, free-standing films of solid polymer electrolytes were prepared using a trifunctional crosslinking agent. The electrochemical characteristics of some of these new materials, including their performance in lithium batteries, are reported and discussed

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The plastic deformation of a highly crosslinked glassy polymer, poly(diethylene glycol bis(allyl carbonate)) (ADC resin) at different temperatures was investigated. It is found that both compressive yield stress O-y and Young's modulus E decrease as temperature is increased. The relationship between try and E has been analysed using Argon's and Bowden's theories of plastic deformation in glassy polymers. Molecular parameters derived from each theory have been discussed in terms of the chemical structure of the resin.

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Water-soluble terpolymers of acrylamide, acrylic acid and N-[(4-decyl)phenyl]acrylamide have been synthesized by a miceilar polymerization technique. Neutralization of the acid groups after polymerization yields hydrophobically modified polyelectrolytes. The ratio of the surfactant to the hydrophobic comonomer (SMR) was varied in successive polymerizations to yield a series of terpolymers with varied amphiphilic microstructures. Although each terpolymer in the series was identical in overall composition and molecular dimensions, profound differences in associative behaviour were observed. Terpolymers synthesized at low SMR exhibit large enhancements in viscosity owing to hydrophobic associations in 0.5 M NaCI. Those synthesized at high SMR behave in a similar fashion to a control acrylamide/acrylic acid copolymer. While viscometric studies indicate associative thickening behaviour, pyrene probe fluorescence studies fail to indicate the presence of well-organized hydrophobic microdomains.

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Nitrilotriacetic acid (NTA) coupled with commonly used metal oxidants was used as an initiator for the aqueous polymerization of acrylamide (AM) under neutral or acidic conditions. The cerium(IV)-NTA pair under neutral conditions behaved as the most promising redox initiator. In order to find the mechanism of generation of free radicals and to determine the complex formation constant (K) and the disproportionation constant (kd), blank tests for the reactions of Ce(IV) with NTA were conducted under conditions of neutral, 1 N HNO3 and 1 N NaNO3, respectively. The mechanism was further confirmed by 3C and t H n.m.r, spectra and the kinetic parameters for the aqueous polymerization of AM were evaluated. The effects of additives on the polymerization were studied and the use of the Ce(IV)--NTA redox pair for other aqueous polymerization systems such as acrylic acid (AA), acrylonitrile (AN) and methyl methacrylate (MMA) was also studied

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Following Kramer et al. who compared the maximum local draw ratio inside craze fibrils or shear deformation zones for different types of network structures, here the critical thickness (IDc), below which apparently brittle amorphous glassy polymers demonstrate a macroscopic draw ratio comparable with the high values determined on a microscopic scale, is studied for two -- principally different -- types of physical networks. The value of ID e is determined for network structures based on polystyrene-poly(2,6-dimethyl- 1,4-phenylene ether) (PS-PPE) blends. Two types of networks are compared obtained via blending high molecular weight PPE with either (i) a (standard) high molecular weight PS (PSh) or (ii) an extremely low molecular weight PS (PSI). In contrast to PSh, PS 1 cannot contribute to the entanglement network structure of the blend since the molecular weight falls well below the entanglement molecular weight of PPE and, consequently, it can be considered as a (glassy) solvent for PPE. The critical thickness of two network structures with the same network density but with different values of the natural draw ratio (2max) is experimentally determined via addition of (non-adhering) core-shell rubbers. IDc proves to be inversely proportional to the natural draw ratio of the network structure. The simple energy-based model for the prediction of ID? quantitatively explains the differences found.

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